城市群热岛时空特征与地表生物物理参数的关系研究

Study on Urban Heat Island Effects and Its Associated Surface Indicators

以长株潭城市群区域为例,利用2005年3个不同季节的TERRA/MODIS数据提取的地表温度、归一化植被指数（NDVI）和归一化建筑指数（NDBI）,分析了城市热岛效应及其随季节的变化,采用归一化植被指数（NDVI）和归一化建筑指数（NDBI）作为反映地表生物物理特征的参数,分析了城市热岛时空特征与地表生物物理参数的关系。研究结果表明,研究区域城市热岛效应的季相变化明显,一年中夏季与春季的城市热岛效应相对显著,城市地表温度高出周边的郊区达8~10℃;而冬季城市热岛效应相对不太明显,城市地表温度高出周边的郊区4℃。地表温度与归一化植被指数（NDVI）的相关性随季节变化较为明显,说明通常将归一化植被指数（NDVI）作为城市地表温度或城市热岛的代用指标是不适宜的;然而,地表温度与归一化建筑指数（NDBI）在不同季节都呈显著的线性关系,而且地表温度与NDBI线性关系的斜率和截距能够很好地指示不同季节城市热岛的强度,这就为定量分析不同季节城市地表温度的变化提供了物理指数,也为利用遥感研究城市热岛效应提供了新的方法与途径。

This study assesses surface urban heat island（UHI） and its associated surface physical characteristics using remote sensing approaches.TERRA/MODIS images acquired in 2005 in three different seasons were selected to generate land surface temperature and surface characteristics for the Changsha-Zhuzhou-Xiangtan metropolitan area in China.The intensity of urban heat island effects and its seasonal variations were examined.The result showed that UHI effects were significant both in the summer and the spring.Land surface temperatures in the city were 8℃ to 10℃ warmer than those in surrounding rural areas in the spring and the summer seasons.Although UHI effects existed in the winter,they are not as significant.Land surface temperature in the city was 4℃ warmer than that in surrounding rural areas in winter.This study uses normalized difference vegetation index（NDVI） and normalized difference built-up index（NDBI） as indicators of surface physical characteristics and investigates the relationship between land surface temperature（LST）,NDVI,and NDBI.Results from this study indicate that,while the relationship between LST and NDVI changes in different seasons,there is a strong positive linear relationship between NDBI and LST for all seasons.The amount of slope and intercept of linear relationship between NDBI and LST can indicate the magnitude of UHI for different seasons.This finding suggests that NDBI provides an alternative physical indicator for analyzing LST quantitatively over different seasons,and therefore providing a useful way to study UHI effects using remote sensing.